1. Field of the Invention
The present invention relates generally to a drug delivery apparatus and method, and more particularly, to an apparatus and method for selectively and locally delivering a drug to internal body tissue.
2. Description of the Prior Art
Many techniques currently exist for delivering drugs or other medicaments to body tissue. These include, among possible others, oral administration, injection directly into body tissue such as through an intramuscular injection or the like, topical or transcutaneous administration where the drug is passively absorbed, or caused to pass, into or across the skin or other surface tissue and intravenous administration which involves introducing a selected drug directly into the blood stream.
Except for topical or transcutaneous administration, the above drug delivery systems tend to be systemic. In other words, administration of the drug is delivered throughout the body by the blood stream.
Over the past several years, the pursuit of devices for localized drug delivery has become exceedingly more intense as the advantages of this method of therapy over systemic drug administration have become apparent. Because many diseases affect a specific site or organ within the body, it is advantageous to preferentially treat the affected area. This avoids high systemic drug levels which may result in adverse side effects and concentrates therapeutic agents in the local area where they are needed. By treating just the diseased tissue, the total quantity of drug used may be significantly reduced, and hence the cost of therapy, especially when using newer genetically engineered drugs. Moreover, local drug delivery may allow for the use of certain effective therapeutic agents which have previously been considered too toxic or nonspecific to use systemically.
Several devices have been developed for the purpose of accessing specific body lumens or passageways (i.e., blood vessels, gastrointestinal tract, urinary tract) and delivering therapeutic agents transmurally to specific subregions of tissue. A double-balloon catheter has been used to administer agents to the area confined by the balloons. A disadvantage of this system is that drugs may be lost through communicating vessels between the balloons. Alternatively, a perforated balloon has been developed to deliver agents directly into the vessel wall. A major disadvantage with both of these systems in certain desired applications is that the drug is delivered radially in all directions.
In some therapeutic applications, it can be advantageous to deliver the drug only to one radial section of the vessel or passageway. For example, localized neoplasia in the gastrointestinal, urinary or reproductive tracts often encompass only a portion of the lumenal circumference. The ducts of the prostate gland communicate with the floor of the urethra; therefore, it would be more efficient to deliver agents (antibiotics, anticancer agents) toward the ducts which access the prostate than to circumferentially deliver across the prostatic urethra.
Therefore, a need exists for a drug delivery apparatus providing radially restricted delivery of a drug or medicant to a localized area of internal body tissue.